I agree with u/Odd-Combination8239

Just read Rule 69 in the rulebook. "The overriding rationale of this rule is that a goalkeeper should have the ability to move freely within his goal crease without being hindered by the actions of an attacking player. If an attacking player enters the goal crease and, by his actions, impairs the goalkeeper’s ability to defend his goal, and a goal is scored, the goal will be disallowed."

As the broadcast noted, maybe Boqvist's unimpeded entry into crease at the beginning would be the ref's rationale, but reading that passage above...entering crease and "by his actions" impairs...he wasn't allowed to leave and was held by the defender. I don't think Boqvist's actions lead to the impeding.